Tuning unit



J. P. PUTNAM Jan. 5, I937.

TUNING UNI T Filed Sept. 22, 1934 SSheets-Sheet l Fig-4- i'jfgLVENTCIR 5 PM. ATTDRNE'LI:

J. P. PUTNAM Jan. 5, 1937.

TUNING UNIT Filed Sept. 22, 1934 3 Sheets-Sheet 2 Jan. 5, 1937.

Filed Sept. 22, 1934 J. P. PUTNAM TUNING UNIT 3 Sheets-Sheet 3 Patented Jan. 5, 1937 UNITED STATES PATENT OFFICE TUNING UNIT Application September 22, 1934, Serial No. 745,097

13 Claims.

This invention relates to tuning units for electric circuits and is adapted for use in radio systems, oscillator circuits, test oscillators and the like.

As is well understood by those skilled in the art it is advantageous totune a circuit in such manner as to keep the ratio of inductance to capacity constant over the whole tuning range rather than to employ a variable inductance and fixed capacity or variable capacity and fixed inductance. Heretofore variable inductances used for tuning circuits have been unduly bulky, as well as otherwise objectionable, and in the systems in general use today a fixed inductance and variable capacity are employed chiefly to reduce the cost of construction and the size or physical bulk of the apparatus. To cover a much greater frequency range than the broadcast band, a variable inductance in the tuned circuit is essential. For most satisfactory operation of a tuned circuit, a smoothly-variable inductor used in conjunction with a variable capacitor is desirable.

It is therefore the primary object of my invention to provide a tuning unit comprising a unitary self-contained structure embodying such smoothly-variable inductor and capacitor.

Further objects are to eliminate the metallic cans heretofore employed for shielding the inductor from extraneous electrical forces and arrange the inductor and capacitor in such way that the latter performs the function of a partial shield for the former, to effect the greatest possible economy of sizeand weight, to reduce the cost of construction to a minimum, and to eliminate the necessity for a condenser shaft and the various means heretofore employed, such as tapped coils, switches and the like for varying the inductance.

Various other objects and advantages of my invention will appear in the detailed description of the exemplification. thereof shown in the drawings.

For effecting the desired objects, my invention comprises a variometer, preferably spherical, tothe rotor of which is fixedly connected the rotor of a variable condenser. By the word variometer as used in this specification and the appended claims I desire to be understood as\ meaning an inductor comprising a plurality of conductively-connected, inductively-related, relatively-movable windings. The stator of the condenser is connected between parallel metal plates which afford bearings for the variometer and condenser rotor unit and, where a plurality of such units are employed, act as shields for each unit. My invention comprises also means whereby successive units may be locked together by connectors attached to the variometer rotors, novel means for connecting the tuning unit to the circuit in which it is employed, and various other features hereinafter specifically described.

An illustrative embodiment of my invention is shown in the accompany drawings in which- Figure 1 is a side elevation of my improved tuning unit with the front plate broken away;

Fig. 2 is a plan view;

Fig. 3 is an end elevation;

Fig. 4 is a side elevation of the variometer and its associated condenser, certain parts being shown in section;

Fig. 5 is a vertical section taken on the line 5-5 of Fig. i;

Fig. 6 is an exploded perspective view showing the variometer-stator and its associated gudgeons;

Fig. '7 is an exploded perspective view showing the several parts of the tuning unit;

Fig. 8 is a diagram illustrating one type of circuit in which my tuning unit may be employed;

Fig. 9 is an end elevation, certain parts being shown in section, of one form of my tuning unit adapted for use in an oscillator;

Fig. 10 is a fragmentary sectional view illustrating my preferred means for locking adjacent units together;

Fig. 11 is a fragmentary sectional view of a detail of construction; I

Fig. 12 is a diagram representing an oscillator circuit with the tuning unit shown in Fig. 9 incorporated therein.

In the particular drawings selected for more fully disclosing the principle of my invention and which are to be considered as illustrative merely and not restrictive, It is a stator consisting in the present instance of a spherical body formed of insulating material and having a central passage H therethrough, together with holes at right angles to said passage for receiving the metallic gudgeons l2, l2 on which the rotor is mounted.

The rotor l3 comprises a split casing l4, it, each half of which has a spherical interior surface and a central passage registering in initial position with the passage ll of the rotor, as shown in Fig. 4. Two opposite ends of the proximate surfaces of the rotor casing are provided with semi-cylindrical depressions l5, l5 for receiving the stator gudgeons and secured to the other ends thereof are metal clips 5 which, when the rotor halves are fastened together by the bolts I1, press against and make electrical contact with the stator gudgeons.

Stator coils [B of any suitable type, and preferably of the type known as universal or crosswound coils, are applied, as for example by cementing, to the exterior spherical surface of the stator while similar coils l9 are applied to the interior spherical surface of the rotor. The several coils of the variometer are connected together in any of the usual well-known ways. As indicated in Fig. 5 a series connection is used in the present instance.

Secured to the lower half of the variometerrotor frame is a condenser-rotor 20, the blades of which are semi-circular in form, with the central portions thereof removed. As such portions are identic in size and position there is formed a trough or hollow extending longitudinally of the condenser-rotor at right angles to the plane of each blade thereof. In the present instance the cut-out portion of each blade is bounded by two parallel lines normal to the linear edge of the blade and by an arc concentric with the arcuate edge thereof (Fig. 1). Obviously the shape of the central cut-away portions of the blades and the resulting trough or hollow aforesaid is immaterial. In the particular drawings herein described the variometer-rotor is provided with flanges 2|, to which the condenser-rotor blades are secured by bolts 22, and the lower portion of said variometer-rotor is disposed within the trough or hollow formed, as aforesaid, in the condenser-rotor (Fig. 7.) A suitable frame herein shown as a pair of parallel metallic plates 30, held in spaced relation by the studs 3|, is provided for supporting the condenser-stator 32 and affording bearings for the variometer-rotor. The blades of the condenserstator are shown as trapezoidal in shape, with a semi-circular piece removed from the central portion of each (Fig. 1). As such central portions are identical in size and position, there is formed a semi-circular trough or hollow extending longitudinally of the condenser-stator at right angles to the plane of each blade thereof for accommodating the lower portion of the variometer-rotor disposed as aforesaid in the trough formed in the condenser-rotor (Fig. 3).

As indicated in Fig. 1 the condenser-stator blades are secured within the frame by the bolts 33, said blades, as well as the rotor blades being held in spaced :relation, respectively, by the separators 34, 35, respectively.

In the illustrated embodiment of the invention, the variometer rotor is mounted in the frame by means of the disc 36 (Fig. 5) which is secured to the semi-circular projection 31 integral with the upper half of the variometer-rotor, the securing means being indicated as the screws 38, 38, and the disc 39 which is secured to the semicircular projection 4|], integral with the lower half of the variometer-rotor. Ball-bearings may be provided, as indicated in Fig. 2. Anti-friction balls 4| are disposed in a raceway formed in said disc 39 and the adjacent portion of the frame member 30. The disc 36 is provided with a recess 42 in which is disposed an anti-friction ball 43 retained in position by the resilient strip 44 secured to the frame by the screws 45, 45. For rotating the variometer and condenser-rotor unit, a knob 46 attached to the disc 39 and projecting through the frame may be employed.

By disposing the inductor and capacitor in the manner described the latter acts as a partial shield for the former and the parallel plates 30 shield each inductor from the others, thereby eliminating the metal cans heretofore used to enclose each inductor. By the co-axial mechanical connection of the condenser and variometer-rotors the necessity for a condenser shaft is obviated, thereby reducing the bulk of the unit, as the space thus saved is used to house the variometer.

While I have described with some detail the specific exemplification of the invention illustrated in Figs. 1, 2 and 3 showing the embodiment thereof in a single unit which has many uses in the electric arts, it is to be understood that the salient feature of said invention is the arrangement of the variometer and condenser in such manner that no condenser shaft is required and the condenser acts as a partial shield for the variometer. By this arrangement not only is the physical bulk and weight of the apparatus reduced but also the cost of construction is lessened. When a number of such units are employed as in a radio-receiving set, other advantages are secured, as will now be explained.

Heretofore when circuits were tuned by simul taneously varying the capacity and inductance to maintain the inductance-capacity ratio constant over the whole tuning range, the inductors and capacitors were disposed along a shaft and rigidly connected thereto, thereby greatly increasing the bulk of the apparatus already made large by the amount of wire required for the variometers of the prior art. By means of the present invention, however, not only is the size of the tuning unit reduced but the necessity for an independent mechanical coupling between the variometer and the condenser, as well as between successive tuning units when ganged together, is eliminated.

When my invention is used in radio receiving systems a plurality of tuning units ordinarily will be employed, each consisting of a pair of spaced parallel metal plates, enclosing a variometer and condenser. and every plate except the outer plates of the end units constituting the dividing partition between two adjacent units. arranged for by the following simple expedients. viz, the screws 50 which secure the frame-members and studs 3! together are removed and the studs 5! of the adjacent unit threaded, as indicated at 52, to pass through the opening in the plate 3!! and make threaded engagement with the tapped hole in the stud 3|, and each variometer-rotor is provided with a connector to c0- operate with the variometer-rotor of the next adjacent unit whereby the variometer rotors arc locked together in tandem for rotation as a whole. The particular type of connectors shown in the drawings are the pins 53 extending from the semi-circular projection 40 integral with the lower half of the stator and taking into holes 54 in the disc 36 secured to the projection 31 of the upper half of the next adjacent variometerrotor.

For connecting the movable member of the tuning unit to the circuit in which it is employed I prefer to use a clevis 60 secured to the pin El passing through the semi-cylindrical projection Ml and a resilient conducting member 62, herein shown as a helical spring, is connected between the link 63 pivoted to said clevis and a terminal member 64 secured to and insulated from the frame, a lead 65 connecting said pin with one of the variometer windings.

In the present exemplification of the invention the other circuit terminal 66 of the tuning This is .ferred by me for use in such oscillator.

unit is connected to the variometer through the extension 6'! of one of the gudgeons l2 (Fig. 6).

A convenient inductance trim is afforded by the pin 19 against which the block H secured to said extension 6'! is held in contact by the spring '52. By turning said screw the radial position of the variometer-stator may be adjusted.

In Fig. 8 I show one of the usual tuned radioreceiving circuits having my tuning unit incorporated therein. It will be noted that the variometer and condenser afford an impedance coupling between the stages of the system.

In Fig. 12 I have illustrated the application of my tuning unit to an oscillator, for example, the oscillator of the usual superheterodyne and in Fig. 9 is shown the form of my invention pre Generally speaking, the construction shown in Fig. 9 is identical with that already described with the following exceptions: Tickler coils 80, 80 are mounted on the hubs 8| integral with the outer surfaces of the variometer-rotor, sail coils being of course in inductive relation to the variometer coils, and additional clevises 82 and springs and links, such as the spring 62 and link 63 above described, are used for connecting said coils to the oscillator circuit. An oscillator employing my invention will oscillate more uniformly over its range than one of the conventional type which oscillates more vigorously at the higher frequency end of its range,

One of the advantages of my invention is that an extremely wide frequency range can be covered, for example, a range of about eight to one, taking in the airplane beacon and broadcast bands, without discontinuity by a half-turn of the varicmeterrotor. The inductance ratio of the variometer having its coils serially connected is high, being of the order 10 to 1. Obviously such ratio, as well as the frequency coverage may be increased by connecting variometer coils in multiple, or series multiple.

In using this invention in test oscillators, units of different frequency ranges my be ganged together and switched into circuit successively as desired.

Having thus described illustrative embodiments of my invention, without however limiting the same thereto, what I claim and desire to secure by Letters Patent is:

l. A tuning element comprising in combination, an inductor, a rotatable frame enclosing and supporting the same, a condenser having a rotor and a stator, means directly attaching the condenser-rotor to said frame in a manner to partially shield said inductor from extraneous electrical forces and means electrically connecting said inductor and condenser.

2. A tuning unit comprising in combination, a spherical variometer, a rotatable frame enclosing and supporting the same, a condenser rotor, said condenser rotor being attached directly to said frame and partially surrounding the same and the variometer supported thereby and means electrically connecting said variometer and condenser rotor.

3. A tuning unit comprising in combination, a variometer having a rotor and a stator, a rotatable casing supporting and enclosing the variometer rotor, a condenser having a rotor and a stator, means directly attaching the condenser rotor to said casing, the condenser rotor surrounding a portion of said casing and the variometer rotor enclosed therein and means electrically connecting said variometer and condenser.

4. The combination with a variometer cornprising a rotor winding having a spherical interior surface enclosing and mounted for rotation about a stator winding having a spherical exterior surface, of a rotatable casing supporting and enclosing the variometer rotor, a condenser having a rotor and a stator, and means directly attaching the condenser rotor to said casing, said condenser rotor partially enclosing said casing and the variometer rotor enclosed therein.

5. A tuning unit comprising a pair of spaced parallel metallic plates, means holding said plates in spaced relation, a variometer having a rotor and a stator, a condenser having a rotor and a stator, means directly attaching the condenser rotor to the variometer rotor for coaxial rotation therewith within the space bounded by said plates, the condenser rotor partially enclosing the variometer rotor, and means mounting the variometer rotor for rotation in and between said parallel plates.

6. In a radio receiver, a plurality of tuning units, each unit comprising a variometer having a rotor and a stator, one enclosing the other, and a condenser having a plurality of interleaved rotor and stator blades, means directly attaching the condenser rotor of each unit to the variometer rotor thereof for coaxial rotation therewith, a plurality of support members, means mounting each variometer rotor for rotation in and between two of said support members, and means carried by the variometer rotors for looking the same in tandem for rotation as a whole.

'7. In a radio receiver, a plurality of tuning units, each comprising a variometer having a rotor and a stator, one enclosing the other, and a condenser having a plurality of interleaved rotor and stator blades, means directly attaching the condenser rotor of each unit to the variometer rotor thereof for coaxial rotation therewith, a plurality of parallel support members, means mounting each variometer rotor for rotation in and between two of said support members, and connectors attached to each variometer rotor and disposed for co-operation with the variometer rotor next adjacent for looking said variometer rotors together in tandem for rotation as a whole.

8. A tuning unit comprising in combination, a variometer having a split casing, each half of said casing having a hemispherical cavity, a winding disposed on the surface of each said cavity, a spherical member disposed within the spherical cavity formed by the cavities in the two portions of said casing, a winding on the surface of said member, means securing the two halves of said casing together, means mounting said casing and said member for relative rotary movement, a rotary condenser having a plurality of rotor and stator blades, and means directly attaching the rotor blades of said condenser to one of the halves of said casing, the plane of each said blade being normal to the plane of the proximate faces of the two halves of said casing.

9. A tuning unit comprising in, combination, a variometer having a split casing, each half of said casing having a hemispherical cavity, a winding disposed on the surface of each said cavity, a spherical member disposed within the spherical cavity formed by the cavities in the two portions of said casing, a winding on the surface of said member, means securing the two halves of said casing together, means mounting said casing and said member for relative rotary movement, a rotary condenser having a plurality of rotor and stator blades, the rotor of said condenser having a longitudinally-extending, centrally-disposed trough formed therein, and means directly attaching the rotor blades of said condenser to one of the halves of said casing, the plane of each said blade being normal to the plane of the proximate faces of the two halves of said casing and a portion of said casing being disposed within said trough.

10. A tuning unit comprising in combination, a variometer having a rotor and a stator, a rotatable casing supporting and enclosing said rotor a condenser having a rotor and a stator each comprising a plurality of blades, means mounting the variometer rotor for rotation with respect to the variometer stator, and means directly attaching the blades of the condenser rotor to said casing for co-axial rotation therewith.

11. In a tuning unit, a condenser rotor having a plurality of plates, said condenser rotor having means defining a centrally disposed interior recess, a variometer rotor, a rotatable casing supporting and enclosing said variometer rotor, a portion of said casing being disposed within said recess, and means securing said condenser rotor to said casing.

12. A tuning unit comprising in combination a variometer having a rotor and a stator, a rotary frame supporting the variometer rotor, a condenser having a rotor and a stator, and means attaching the condenser rotor to the variometer rotor for coaxial rotation therewith within the space bounded by planes normal to the axis of said rotors and contiguous to the ends of said frame.

13. In a radio receiver, a plurality of tuning units each comprising an inductor having a rotor and a stator, a capacitor having a rotor and a stator, means directly attaching the capacitor rotor of each unit to the inductor rotor thereof for rotation about the inductor stator of such unit, a plurality of support members, means mounting each inductor rotor for rotation in and between said support members, and means carried by the inductor rotors for looking the same in tandem for simultaneous ro tation.

JOHN P. PUTNAM. 

